Pharmacological Dissection of High Voltage-Activated Ca 2+ Current Types in Acutely-Dissociated Rat Supraoptic Magnocellular Neurons. Foehring, R. C. and W.E. Armstrong. Department of Anatomy and Neurobiology, University of Tennessee, Memphis, Memphis, TN 38163.
APStracts 3:0043N, 1996.
1. We used pharmacological blockers and whole cell voltage-clamp recordings from acutely dissociated magnocellular neurons from the rat supraoptic nucleus to test for the presence of L-, N-, P-, Q-, and R-type calcium currents. 2. We found clear evidence for L- (dihydropyridine-sensitive), N- (blocked by w - conotoxin GVIA, and P-type (blocked by w -agatoxin IVA) currents. Nifedipine blocked 28 + 2 % of the current, w -conotoxin GVIA blocked 26 + 4 %, and w - agatoxin IVA (25-30 nM) blocked 17 + 4% of the current. In addition, w - conotoxin MVIIC blocked about half (54 + 2%) of the current remaining after L- , N-, and P-type currents were blocked, suggesting the presence of Q-type currents. 3. About 20% of the whole cell current was unblocked by the combination of all four blockers, suggesting the presence of a fifth current type. This residual current inactivated slowly at -10 mV.

Received 23 October 1995; accepted in final form 14 February 1996.
APS Manuscript Number J711-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 March 96